Field of the Invention
The present invention relates to an image forming apparatus that forms an image on a recording medium.
Description of the Related Art
A sheet that has been subjected to printing by an image forming apparatus is sometimes subjected to post-processing by a post-processing apparatus. The amount of time it takes to perform post-processing is sometimes longer than the amount of time it takes to form an image on a sheet. For this reason, the image forming apparatus discharges a successive sheet to the post-processing apparatus after waiting until the post-processing of a preceding sheet is complete. Post-processing is also sometimes applied to a sheet that has been subjected to double-sided printing. Japanese Patent Laid-Open No. 2014-73630 proposes that an interval between a sheet that has been subjected to second-surface printing and a sheet that is to be newly fed from a feeding unit in order to undergo printing on its first surface is set according to the processing time amount for post-processing applied to the sheet resulting from second-surface printing. Japanese Patent Laid-Open 2014-73630 also proposes that printing on a first surface of a sheet fed from a feeding unit and printing on a second surface of a sheet on whose first surface an image has already been formed are executed alternatingly. Thus, in the invention disclosed in Japanese Patent Laid-Open No. 2014-73630, the interval at which sheets are fed from the feeding unit is determined based on the amount of post-processing time, and thereby the interval between a sheet being fed from the feeding unit and a sheet that has been subjected to first-surface printing is determined.
Incidentally, depending on the amount of post-processing time, there are cases where the sheet that has been subjected to first-surface printing needs to wait on the conveyance path, but no consideration is given to this in the invention disclosed in Japanese Patent Laid-Open No. 2014-73630. As a result, a sheet that has been subjected to first-surface printing and is re-fed to the image forming unit for second-surface printing ends up colliding with a sheet fed from the feeding unit to the image forming unit for first-surface printing. Such collisions are particularly likely to occur in cases where the amount of post-processing time varies.